1. Field of the Invention
The present invention relates to modular chimney systems and, more particularly, to a modular chimney flue construction that does not require a flue lining and does not deteriorate with heating and cooling.
2. Background Art
The design and construction of an efficient, functional fireplace requires adherence to some basic rules concerning dimensions and the placement of various component parts. The objectives of a correctly designed fireplace are to: (1) assure proper combustion of the fuel; (2) deliver smoke and other products of combustion up the chimney; (3) radiate the maximum amount of heat into the room; and (4) afford simplicity and fire safety in construction.
The first of the two objectives are closely related and depend mainly upon the shape and dimensions of the combustion chambers, the proper locating of the fireplace throat and the smoke shelf, and the ratio of the chimney flue area to the area of the fireplace opening. The third objective depends upon the dimensions of the combustion chamber, while the fourth depends upon the size and shape of the masonry units and their ability to withstand high temperatures without warping, cracking or deterioration.
The shape of the combustion chamber influences both the draft and the amount of heat that will be radiated into the room. The slope at the back throws the flame forward and leads the gases with increasing velocity through the fireplace throat and into the chimney flue. It is desirable, for the proper draw of products of combustion up the chimney, to obtain relatively high velocities of through the fireplace throat and the chimney flue. The velocities of combustion products is reduced, with a corresponding decrease in energy efficiency of the fireplace, if the chimney flue surface of the chimney has other openings, connections, or is rough.
Older methods of chimney construction, such as brick and mortar construction, typically result in a rough textured surface as if is difficult to maintain a smooth surface with the multitude of joints that result from the brick and mortar construction. Hence, the use of a flue lining is recommended for these types of chimney construction in order to provide a smooth interior surface and thereby provide a more efficient operation of the flue. An additional problem that plagues brick and mortar chimneys without flue linings is that portions of the chimney may have to be rebuilt every few years due to the disintegrating effect of smoke and gases on the mortar. This is a costly repair as the brick chimney must be taken down to a point where the mortar joints are solid and a new top rebuilt. This disintegration of an unlined chimney also poses a safety hazard as products of combustion can escape the confines of the chimney flue into the surrounding construction materials, which are typically wood frame construction, thus causing a fire safety hazard.
A chimney made of brick, with a flue liner to increase efficiency, is a difficult and costly construction. Flue liner sections are typically mortared, with a simple butt joint, onto the proceeding flue liner before the brickwork has reached the top of the flue liner section below, and then the brick built up around them. Where offsets or bends are necessary in the chimney, they are normally formed by equally mitering both ends of abutting sections of flue lining in order to prevent any reduction of the flue area, since it is important that the same effective flue area be maintained the whole height of the flue. The difficulty of making all of the joints in both the flue lining and the surrounding masonry construction free from leaks that can form a safety hazard require the use and expense of a skilled artisan. Any open joint must be repaired and, since such repairs are usually difficult, the expense of a typical brick masonry chimney is compounded.
A chimney made of metal tubing is less expensive to construct than the typical brick and mortar construction. A metal chimney also offers the advantage of providing a smooth surfaced chimney flue. However, a metal chimney does not dissipate heat readily and can present a fire hazard to surrounding construction materials. Also, a metal chimney is susceptible to deterioration over time due to the changing temperature and heat load produced by the fireplace resulting in cracks, leaks and rust in the metal chimney. This deterioration of a metal chimney can cause a fire safety hazard as the chimney warps and moves under the heat load produced by the fireplace, which results in the requirement to eventually remove and replace the metal chimney.
Consequently, there exists a need in the art for a chimney such as a modular chimney construction that does not require a flue liner and that does not deteriorate with heating and cooling, which is nested for structural stability and to ensure a no leak seal so as to eliminate any possible passage of flame through the joints of the modular chimney construction, and allows for proper combustion of the fuel and the efficient delivery of smoke and other products of combustion up the chimney while also providing ease of construction, enhanced fire safety and life expectancy of the chimney construction.